JIT Seek Control for Magnetic Disk Power Reduction
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Solution Overview
Problem
Magnetic disk devices face challenges in reducing power consumption, particularly in seek control methods that do not consider rotation waiting times, limiting the flexibility of VCM current adjustments and impacting access performance.
Innovation Solution
The implementation of a JIT seek control method that adjusts the VCM current waveform and head acceleration based on rotation waiting times, specifically by controlling the absolute value of the VCM current and head acceleration in acceleration and deceleration intervals, reducing power consumption by minimizing the impact of back electromotive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fastest seek control is used that does not consider rotation waiting time, then access performance is improved, but power consumption increases and degree of freedom in adjusting VCM current is reduced
Solution Approach 1:
The patent applies dynamics by making the VCM current waveform adjustable and adaptable. The JIT seek control dynamically modifies the current waveform based on rotation waiting time, allowing the system to transition between different operational modes (fastest seek vs. power-saving seek) depending on real-time conditions, thereby resolving the contradiction between speed and energy consumption.
Solution Approach 2:
The patent changes the parameters of the VCM current waveform (amplitude, duration, shape) based on rotation waiting time. By adjusting these electrical parameters, the system can optimize both access performance and power consumption, transforming the fixed fastest seek approach into a flexible control method that considers multiple factors.
2Use of energy by moving object
If JIT seek control is used that considers rotation waiting time, then power consumption is reduced and degree of freedom in adjusting VCM current is increased, but access performance may be impacted
Solution Approach 1:
The patent implements feedback by using rotation waiting time information to adjust the VCM current waveform. The system receives feedback about the rotational state of the disc and modifies the seek control accordingly, ensuring that power consumption is reduced without significantly compromising access performance. This feedback mechanism allows the system to make informed decisions about current waveform adjustment.
3Use of energy by moving object
If VCM current waveform is adjusted to reduce power consumption, then energy efficiency is improved, but control complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal current waveforms for different rotation waiting time scenarios. Instead of performing complex real-time calculations during seek operations, the system prepares control parameters in advance, simplifying the actual control process while maintaining energy efficiency. This approach reduces control complexity by replacing complex runtime computation with pre-prepared solutions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces power consumption by up to 2.5% in 15% distance seeks on magnetic disks while maintaining access performance, by optimizing the VCM current waveform to account for rotation waiting times and back electromotive forces.
Implementation Method 1
a voice coil motor (VCM) 13
Implementation Method 2
in consideration of a back electromotive voltage
Data Source
AI summary
According to one embodiment, a magnetic disk device comprises a JIT seek control unit, which uses second time series data of a current indication value of a VCM that sets a slope having an absolute value smaller than an absolute value of a slope of a first time series data in at least one of a monotonically decreasing interval of an acceleration interval and a monotonically decreasing interval of a deceleration interval of a head or an operation acceleration of the head.